package Text2;

import java.util.*;
public class Main {
    public static void main1(String[] args) {
        int n=0,m=0;
        Scanner in=new Scanner(System.in);
        n=in.nextInt();
        m=in.nextInt();
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i]=in.nextInt();
        }
        while(m>0){
            m--;
            int x=in.nextInt();
            int l=0,r=n-1;
            while(l<r){
                int mid=l+r>>1;
                if(arr[mid]>=x){
                    r=mid;
                }else{
                    l=mid+1;
                }
            }

            if(arr[l]!=x){
               System.out.println("-1 -1");
            }else{
                System.out.print(l+" ");
                l=0;
                r=n-1;
                while(l<r){
                    int mid=l+r+1>>1;
                    if(arr[mid]<=x){
                        l=mid;
                    }else{
                        r=mid-1;
                    }
                }
                System.out.print(l);
                System.out.println();
            }
        }
    }


    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        double x=in.nextDouble();
        double l=-10000,r=10000;
        while (r-l>1e-8){
            double mid=(l+r)/2;
            if(mid*mid*mid>=x){
                r=mid;
            }else{
                l=mid;
            }
        }
        System.out.printf("%.6f",l);
    }
}
